As disclosed in Japanese Patent Application Publication No. 2014-219699, there is conventionally known an image forming device including a fixing device. The fixing device is configured to heat a recording sheet while nipping the recording sheet between a fixing roller and a pressure roller to thermally fix a developer image on the recording sheet. The fixing device is provided with a pressure roller unit, a cam, a coil spring, and a drive source.
The pressure roller unit holds the pressure roller such that the pressure roller can be displaced between a pressure contact position (second pressure state) and a separation position (non-pressure state). In the pressure contact position, the pressure roller is in pressure contact with the fixing roller. In the separation position, the pressure roller is separated from the fixing roller. The cam is rotatable about an axis of a cam shaft in both a counterclockwise direction and a clockwise direction. The counterclockwise direction is an example of a first direction, and the clockwise direction is an example of a second direction. The cam has a cam surface. The distance between the cam surface and the axis of the cam shaft is reduced in the clockwise direction. The coil spring urges the pressure roller unit in an urging direction to bring the pressure roller toward the cam surface. The drive source generates a driving force to rotate the cam in both the counterclockwise direction and the clockwise direction.
When the cam is driven by the drive source to rotate in the counterclockwise direction, the cam surface allows the pressure roller unit to be displaced in the urging direction. Hence, the pressure roller is displaced to the separation position. On the other hand, when the cam is driven by the drive source to rotate in the clockwise direction, the cam surface pushes the pressure roller unit in a direction opposite to the urging direction. Hence, the pressure roller is displaced to the pressure contact position.